Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1999-02-17
2002-08-20
Sellers, Robert E. L. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C065S111000, C065S425000
Reexamination Certificate
active
06437054
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a molding composition comprising a polyester ionomer resin and a polyamide resin.
BACKGROUND OF THE INVENTION
Blending of an aromatic polyester resin and a polyamide resin offers the advantage of reduced moisture absorption compared to pure polyamide and higher heat compared to pure aromatic polyester. However, such blends are incompatible resulting in poor surface appearance, delamination, poor ductility, and difficult injection molding. The advantage of incorporating sulfonate salt groups into a poly(1,4-butulene terephthalate) polyester is that the sulfonate groups impart inherent compatibility between the sulfonated polyester ionomer and polyamide resulting in improved surface appearance, reduced delamination, and improved processability. However the blends still are britt;e with poor elongation.
U.S. Pat. No. 4,097,446 to Abolins and Holub discloses a wide variety of blends of different thermoplastic resins with a very rapidly crystallizing polyester; namely polybutylene terephthalate and fiber glass. Nylon is shown as an example of a suitable blend resin. Fiber glass is important in obtaining improved processability.
U.S. Pat. No. 5,300,572 to Tajima, et al. relates to moldable polyester resin compositions which include the resin components: (A) between 2 to 98% by weight of a compatibilizing metal sulfonate group-containing aromatic polyester copolymer which is the polycondensation reaction product of (a) an aromatic dicarboxylic acid or its ester-forming derivative, (b) a diol compound or its ester-forming derivative, and (c) an ester-forming compound containing a metal sulfonate group; (B) between 2 to 98% by weight of an additive resin which is one of (B-I) an olefin copolymer which is the copolymerization reaction product between an olefin with at least one of an alpha,.beta.-unsaturated carboxylic acid or its derivative and a vinyl alcohol or its ester, and (B-II) a polyamide resin; and, optionally (C) between 0 to 96% by weight of a non-compatibilizing aromatic polyester resin.
As set forth in Tajiima, et al. the modified aromatic polyester copolymer having metal-sulfonate-containing units introduced into the copolymer's backbone structure of aromatic polyester copolymer is compatible with both polyolefin and polyamide resins, and serves as a compatibilizer when an unmodified (i.e., one not containing metal-sulfonate units) aromatic polyester is further blended with the modified polyester copolymer and either a polyolefin or a polyamide resin.
A problem with blends of comprising a polyester ionomer resin and a polyamide resin is the lack of ductility. Despite improved compatibilization of the polyamide blend with the polyester sulfonate salt, leading to finer morphology and better appearance than a blend of nylon with a standard thermoplastic polyester, the blends show poor elongation and impact. The melt strength is also deficient for processes like blow molding, profile extrusion and thermoforming. An additional problem may be encountered if the polyester ionomer and polyamide resin blend is not dried well before processing. Hydrolysis may cause molecular weight degradation which also may result in a reduction in mechanical properties.
Accordingly, there is a need for improved polyester resin compositions which exhibit improved elongation, good appearance and good melt processing capability.
SUMMARY OF THE INVENTION
We have found that modification of a blend of an aromatic metal sulfonate co-polyester resin and a polyamide resin with an effective amount of at least one difunctional epoxy compound results in improved polyester resin compositions which exhibit consistent and uniform properties, improved elongation at break and good appearance. The resulting blends have good chemical resistance, mechanical properties along with good processability and reduced moisture absorbance.
In accordance with the present invention, there is provided a thermoplastic resin composition having improved elongation and temperature resistance comprising a compatible resin blend of a polyester ionomer and a polyamide and an effective amount of at least one difunctional epoxy compound, said at least one difunctional epoxy compound having at least one cyclohexane ring moiety and having two terminal epoxy functional groups, wherein at least one of the two terminal epoxy functional groups is a substituent on at least one cyclohexane ring moiety; and optionally an effective amount of a catalyst compound.
According to the preferred embodiments, a functional sulfonate salt “ionomer” group is incorporated into the polyester so that a blends of polyester ionomer have improved properties as compared to blends not utilizing the polyester ionomer and not having the epoxy additive.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The term polyester ionomer, or sulfonate polyester or metal sulfonate polyester, refers to polyester polymers derived from the reaction residue of an aryl carboxylic sulfonate salt, an aromatic dicarboxylic acid, an aliphatic diol or any of their ester forming derivatives. The ionomer polyester polymers comprise some monovalent and/or divalent sulfonate salt units represented by the formula IA:
or formula IB:
(M
+n
O
3
S)
d
—A—(OR″OH)
p
wherein p=1-3; d=1-3, and p+d=2-6, and A is an aryl group containing one or more aromatic rings: for example, benzene, naphthalene, anthracene, biphenyl, terphenyl, oxy diphenyl, sulfonyl diphenyl or alkyl diphenyl, where the sulfonate substituent is directly attached to an aryl ring. These groups are incorporated into the polyester through carboxylic ester linkages. The aryl groups may contain one or more sulfonate substituents; d=1-3 and may have one or more carboxylic acid linkages; p=1-3. Groups with one sulfonate substituent (d=1) and two carboxylic linkages (p=2) are preferred. M is a metal, n=1-5. Preferred metals are alkaline or alkaline earth metals where n=1-2. Zinc and tin are also preferred metals. R′ is a alkyl group, for example, —CH
2
CH
2
—, —CH
2
CH
2
OCH
2
CH
2
—, —CH(CH
3
) CH
2
—, —CH
2
CH
2
CH
2
—, —CH
2
CH
2
CH
2
CH
2
—.
Typical sulfonate substituents that can be incorporated into the metal sulfonate polyester copolymer may be derived from the following carboxylic acids or their ester forming derivatives; sodium sulfo isophthalic acid, potassium sulfo terephthalic acid, sodium sulfo naphthalene dicarboxylic acid, calcium sulfo isophthalate, potassium 4,4′-di(carbomethoxy) biphenyl sulfonate, lithium 3,5-di(carbomethoxy)benzene sulfonate, sodium p-carbomethoxy benzene sulfonate, dipotassium 5-carbomethoxy-1,3-disulfonate, sodio 4-sulfo naphthalene-2,7-dicarboxylic acid, 4-lithio sulfophenyl-3,5-dicarboxy benzene sulfonate, 6-sodiosulfo-2-naphthyl-3,5-dicarbomethoxy benzene sulfonate and dimethyl 5-[4-(sodiosulfo) phenoxy] isophthalate. Other suitable sulfonate carboxylic acids and their ester forming derivatives are described in U.S. Pat. Nos. 3,018,272 and 3,546,008 which are included herein by reference. The most preferred sulfonate polyesters are derived from sodium 3,5-dicarbomethoxy benzene sulfonate.
Preferred ionomer polyester polymer comprises divalent ionomer units represented by the formula II:
wherein R is hydrogen, halogen, alkyl or aryl, and M is a metal.
The most preferred polyester ionomer has the formula III:
where the ionomer units, x, are from 0.1-50 mole percent of the polymer with 1.0 to 20 mole percent being preferred. Most preferably R is hydrogen. When R is hydrogen, A
1
is phenylene, and R
1
is an alkylene radical of from C
1
-C
12
, preferably from C
2
or C
4
, and x and y are in mole percent, then x is from about 1 to about 20 percent, and more preferably from about 1 to about 10 percent.
Typical glycol or diol reactants, R
1
, include straight chain, branched, or cycloaliphatic alkane diols and may contain from 2 to 12 carbon atoms. Examples of such diols include but are not limited to ethylene glycol; propylene glycol, i.e., 1,2- and
Bastiaens Josef H. P.
Chisholm Bret J.
Gallucci Robert R.
General Electric Company
Sellers Robert E. L.
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